Lab Diamond Polish and Symmetry: The Complete Guide

Last Updated on July 8, 2023 by Rolf Hartmann

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If you’re in the market for a lab-grown diamond, you may have come across terms like “diamond symmetry” and “diamond polish.” These two factors play an important role in determining a diamond’s beauty and value. In this guide to lab diamond polish and symmetry, we’ll take a closer look at what these terms mean and whether it’s worth paying extra for excellent diamond polish and symmetry.

Understanding polish and symmetry can be complicated, but that’s why we created this simple buying guide to lab diamond polish and symmetry. We will investigate the nuances of lab diamond polish and symmetry to help you make an educated decision when purchasing lab-grown diamonds.

Lab diamond polish and symmetry are two distinct factors in determining diamond quality, but they are often listed together. So, first, we’ll explain what lab diamond polish is and what it means to you when buying lab-grown diamonds. We’ll explore how expert cutters achieve high-quality polish and discuss the grading system used by diamond laboratories such as GIA and IGI.

Next, we’ll look closer at lab diamond symmetry and show what you should look out for. We’ll evaluate the importance of symmetry in maximizing light performance and demonstrate why that matters.

We round off by looking into Triple Ex, which combines the best lab diamond polish, symmetry, and cut grades, and comparing lab diamond polish and symmetry with the lab diamond 4Cs to help you find the perfect lab diamond and save money!

And when you feel equipped to buy your next lab-grown diamond, we recommend the best places to buy lab diamonds.

We’ll continue our guide to lab diamond polish and symmetry by learning about diamond polish.

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Lab diamond polish

Lab diamond polish refers to the quality of a diamond’s surface condition after it has been cut and polished. When diamonds are cut from rough stones, they have natural imperfections that need to be removed by polishing with a jeweler’s torch or polishing wheel.

A well-polished lab-created diamond will have minimal blemishes (external imperfections), such as scratches, nicks, abrasions, pits, lizard skin, or burn marks. These imperfections can impact the overall beauty and brilliance of the stone but do not necessarily indicate poor cutting skills (though some can be cut away).

How are lab diamonds polished?

To achieve an excellent polish on a lab-grown diamond skilled diamond cutters use a polishing wheel coated with fine-grain diamond to accomplish an excellent polish on lab-grown diamond dust. This abrasive material helps re any rough spots from the lab diamond’s surface, also smoothing out its facets. The result is a beautifully polished diamond that sparkles brilliantly when exposed to light.

Common external imperfections found in diamonds

• Natural: Small portions of unpolished rough diamond left on the finished stone.
• Pits: Tiny holes caused by gas bubbles trapped within the crystal during formation.
• Burn Marks: Discoloration or dating from excessive heat exposure during cutting or polishing (e.g., from a jeweler’s torch).
• Lizard Skin: An uneven texture resembling reptile scales caused by irregularities in the crystalline structure.
• Abrasion: Scratches or scuffs along facet junctions due to contact with other diamonds or surfaces during cutting, polishing, or wear.

Evaluating lab diamond polish grades

Determining the polish grade of your lab-grown diamond is an essential step in assessing its overall quality. A good polish features no visible polishing marks on the surface of the stone under 10x magnification.

To accurately evaluate a diamond’s polish, it’s crucial to examine it under natural light using magnification. The Gemological Institute of America (GIA) has established a grading system that ranges from Excellent (Ex) to Poor (Pr) based on observations made by professional gemologists under 10X magnification.

All lab diamonds that are independently graded by reputable diamond institutes, such as GIA or IGI, include polish grading. Therefore, unless you’re looking for smaller accent stones, you should only buy lab-grown diamonds with diamond certificates from a reputable independent grading institute.

Here’s an example of an IGI lab diamond certificate showing the diamond polish grade.

GIA Grading System for Polish

1. Excellent: No visible polishing marks or surface defects when viewed at 10X magnification.
2. Very Good: Minor polishing marks or surface defects visible only at higher magnifications but not noticeable to the naked eye.
3. Good: Polishing features may be slightly visible without magnification but do not significantly impact the diamond’s beauty and brilliance.
4. Fair: Poorly polished surfaces that affect appearance; often accompanied by poor symmetry and cut proportions resulting in reduced sparkle and fire within the stone.
5. Poor: Severe polishing issues such as visible scratches, nicks, and burn marks that significantly detract from the diamond’s overall appearance.

How does lab diamond polish affect brilliance?

The better the quality of your diamond’s polish, the more brilliant it will appear when viewed face-up under normal lighting conditions because there are fewer obstructions between incoming light rays and your eyes. That’s because removing imperfections means that light can pass through without being scattered or distorted by any irregularities on its surface. Conversely, poorly polished diamonds will spread light as it enters, reducing their brilliance.

When looking at lab-grown diamonds online or in-store, keep an eye out for those with high-quality polishes since they tend to reflect more light back up toward you than poorly-polished gems, which makes them appear brighter overall.

Can you see diamond polish with the naked eye?

The short answer is no. In most cases, you won’t be able to assess a lab diamond’s polish grade with the naked eye unless it has an extremely poor rating. However, this doesn’t mean that excellent polish grades are not worth investing in, as they can significantly impact your diamond’s overall beauty and value.

See the below example of a lab-created diamond with only a “Good” polish rating. This magnified video shows some imperfections, but for the untrained, it’s impossible to know what the polish grade should be. (Ritani mostly sells diamonds with an Excellent polish rating, and we recommend looking at one of their other very competitively-priced lab diamonds).

While diamond polish may not be visible to the naked eye, it plays a vital role in determining a diamond’s brilliance and should be considered when purchasing lab-grown diamonds or lab diamond jewelry. Investing in higher-quality polishes will ensure maximum light reflection from your gemstone resulting in more beautiful pieces of jewelry for years to come.

When you buy at reputable lab-grown diamond retailers, you’ll find that many diamonds have Excellent polish. But be sure to always check the grading in the certificate and under product details.

Mined vs. lab diamond polish

When it comes to diamond polish, there is no difference between a mined and a lab-grown diamond. Both types of diamonds undergo the same polishing process to achieve their final shape and appearance.

Lab diamond symmetry

Lab diamond symmetry refers to the precision of a diamond’s surface features and overall diamond shape. It takes into account things like facet alignment, table size, girdle thickness, and culet placement. When these elements are well-proportioned and aligned correctly, they create symmetrical patterns that allow light to reflect evenly throughout the stone.

A higher symmetry rating means that all facets of the diamond are precisely cut with consistent angles and proportions. This results in maximum light return, which makes your diamond sparkle more brilliantly than diamonds with poor or average symmetry ratings.

What is the difference between lab diamond symmetry and cut?

Lab diamond cut and symmetry are two distinct factors that affect the appearance of a diamond. A diamond’s cut grade is determined by its face-up appearance, design, and craftsmanship. Gemologists assess a diamond’s proportion, which includes the size, shape, and angle of each facet, including symmetry. Symmetry, however, only refers to how well the facets are aligned with each other. A diamond with good symmetry will exhibit a superior sparkle compared to one with poor symmetry.

Can you see diamond symmetry with the naked eye?

You may not be able to see asymmetrical diamonds with your naked eye if you’re not an expert in this field. However, asymmetrical diamonds can be noticeable even without magnification as it will affect how much light reflects from different parts of the stone leading to dark areas or dead spots within it.

Here’s an example of a lab-grown diamond with only a “Good” symmetry grading found at one of our favorite jewelers, Ritani (almost all their plan diamonds are graded Excellent. Even looking at the magnified diagram, it can be hard to spot asymmetry. It requires deep expertise to evaluate diamond symmetry.

Why lab diamond symmetry is important

When shopping for lab-grown diamonds or lab-grown diamond jewelry, be sure to pay attention to the symmetry grade listed on their grading report. Look for diamonds that have been graded “excellent” or at least “very good”. It’s also essential to buy from reputable dealers who provide accurate certification as proof of what you are buying.

The benefits of a diamond with a high symmetry grading are:

• Better light performance: Diamonds with good symmetry grades have better fire (flashes of color) and scintillation (sparkles) due to their ability to reflect more light back out through their top surfaces resulting in increased brightness levels.
• Poor polish features: Diamonds with poor polish may have visible polishing marks which detract from their beauty.
• Cut quality: Symmetry also plays a role in the cut quality of your diamond, which is one of the most important factors in determining its overall beauty. A well-cut diamond with good symmetry will have maximum brilliance and fire.

Diamond symmetry categories

Diamond symmetry refers to the precision of a diamond’s surface and shape. And as we have noted, it is an important factor that determines a diamond’s beauty, along with its cut and clarity. A well-symmetrical diamond will have perfect proportions, angles, and facets that reflect light evenly throughout the stone.

Lab diamond symmetry assessment is divided into two categories:

1. Proportion-related assessments focus on how well each facet aligns with its corresponding opposite facet.
2. Facets-related assessments evaluate the shape consistency among similar facets within individual diamonds.

Proportions-related lab diamond symmetry

Proportion-related lab diamond symmetry refers to the precise alignment of a diamond’s facets. A higher symmetry rating indicates that the diamond cutter has skillfully shaped and positioned each facet for optimal light performance. Conversely, asymmetrical diamonds may exhibit poor light reflection or refraction, diminishing their overall beauty.

• Misaligned table/culet: The top and bottom of the diamond are not perfectly aligned.
• Crown/pavilion angle variations: Inconsistencies in angles can affect a diamond’s brilliance.
• Girdle thickness variation: Uneven girdles can lead to durability issues or uneven weight distribution.

Facets-related lab diamond symmetry

Facets-related lab diamond symmetry evaluates the consistency in shape, size, and arrangement of a diamond’s facets. Diamonds with good symmetry will have uniformity across all similar facets, while those with poor symmetry might display irregularities such as extra or missing facets.

• Azimuth shift: Facets deviating from their intended positions around the stone’s circumference.
• Tilted table/facets: Facets that are not parallel to the table or other corresponding facets.
• Non-pointing: Facets that do not meet at a precise point, creating an uneven appearance.

Lab diamond symmetry grades

Like polish grades, lab diamond symmetry grades range from Excellent (Ex) to Poor (Pr), and the grading was created by GIA and is followed by other institutes such as IGI.

• Excellent: At 10x magnification, there are no visible symmetry defects.
• Very Good: At 10x magnification, slight symmetry imperfections can be seen.
• Good: At a magnification of 10x, symmetry defects can be observed but may be acceptable.
• Fair: At 10x magnification, symmetry defects are easily noticeable.
• Poor: At a magnification of 10x, symmetry defects can be easily seen — sometimes even without magnification.

Here’s an example of a GIA lab diamond certificate showing the diamond’s symmetry grade.

Mined vs. lab diamond symmetry

As was the case for lab diamond polish, there is also no difference between a mined diamond and a lab-grown diamond symmetry. Both types of diamonds are cut using similar techniques by skilled craftsmen who use advanced technology like lasers and computer software to achieve precise cuts and aim for perfect symmetry.

Lab diamond polish and symmetry vs. the diamond 4Cs

You may already have heard about the diamond 4Cs, which are the key diamond quality factors that are assessed by grading institutes and jewelers. The diamond 4Cs are precisely the same for mined and lab-grown diamonds since mined and lab-grown diamonds are the same, except for the origin.

The (lab) diamond 4Cs are:

• Cut quality: A diamond’s beauty and brilliance are primarily determined by its cut quality. An ideal or excellent cut allows light to enter the stone, reflect off its facets, and exit through the top of the diamond in a dazzling display. Learn all you need to know about lab diamond cut.
• Clarity: Diamond clarity refers to the absence of inclusions (internal flaws) and blemishes (external imperfections). The fewer, smaller, and less impactful these defects are, the higher a diamond’s clarity rating will be on a scale from Flawless (FL) to Included (I). Read about lab diamond clarity in our guide.
• Color: Lab-grown diamonds come in various shades ranging from colorless (D) to light yellow/brown(Z). Colorless diamonds are considered more valuable because they allow maximum light return, which enhances their sparkle. Learn about lab diamond color and fancy-colored lab diamonds.
• Carat weight: The weight of your lab-grown diamond is measured in carats. Larger stones will be heavier, so weight and size are closely correlated. Bigger diamonds command higher prices due to their rarity, but remember that bigger isn’t always better if it compromises other important aspects like cut or clarity. Read about lab diamond carats.

So what’s more important? Lab diamond polish and symmetry or the diamond 4Cs?

When shopping for a lab-grown diamond, it’s essential to strike the right balance between cut quality, clarity, carat weight, and color grade. While excellent polish and symmetry can enhance a diamond’s beauty, they should not be prioritized at the expense of more critical attributes such as the lab diamond cut grade. But stay clear of any diamond graded below very good on either polish or symmetry. Luckily, with lab-grown diamonds, it’s easy to find affordable diamonds with Excellent polish and symmetry grades that also have great 4C grades, such as Ideal or Excellent cut grades.

What are Triple Ex lab diamonds?

Triple-Ex lab diamonds are those with an excellent cut grade as well as excellent polish and symmetry, hence the 3 Ex(cellent). Broadly speaking, symmetry and polish are not as crucial as diamond cut quality and sometimes not as critical as clarity and color.

That said, it’s still important to consider a lab diamond’s polish and symmetry since they haimpacthe diamond’s appearance and sparkle. And, importantly, it’s an unnecessary compromise on polish and symmetry because, with lab-grown diamonds, you can save up to 60-80% over mined diamonds, making them much more affordable.

What are super ideal diamonds?

Lab diamond sellers such as James Allen and Brilliant Earth offer “super ideal” and “hearts and arrows” cut diamonds that boast exceptional polish and symmetry. These high-quality lab-grown diamonds are crafted precisely to ensure a higher symmetry rating, resulting in a more visually appealing stone. 

However, they can be expensive, and sometimes you can find lab diamonds with “only” ideal cut grades that can be just as good. So make sure to study the diamond images closely.

Tips for buying lab diamonds with excellent polish and symmetry?

We always recommend buying at online jewelers. That’s because they offer a far greater selection at much more competitive prices than traditional brick-and-mortar jewelers. When shopping online, choose trusted retailers who provide high-resolution images/videos showcasing each individual lab diamond available within their inventory, enabling you to discern subtle differences and compare prices.

Tips for choosing a trustworthy lab diamond jeweler

1. Lab diamond certification: Ensure that the retailer offers diamonds with certificates from a reputable and independent diamond institute such as GIA or IGI, which confirm the diamond’s polish, symmetry, cut, clarity, color, and carat weight.
2. Reputation and Reviews: Check customer reviews on reputable platforms like Better Business Bureau (BBB), Google Reviews, Reddit, and, of course, our expert lab diamonds reviews before making a purchase decision.
3. Return policy and warranty: A trustworthy lab diamond seller should have clear return policies and warranties in place. The return policy should be risk-free and at least 30 days. This will give you peace of mind knowing that you are protected if any issues arise after purchasing your lab-grown diamond jewelry piece or if the quality is not as expected.

Where to buy lab diamonds with excellent polish and symmetry?

At LabGrownCarats.com, we review lab-grown diamond jewelers in-depth and compare diamond jewelers.

You can read which we think are the best places to buy lab-grown diamonds and the best places for lab diamond engagement rings.

But, to save time, here are our recommended places to buy lab-grown diamonds with excellent polish and symmetry. In addition to lab diamonds with the highest-rated polish and symmetry grade, they also offer the highest-quality diamonds and jewelry, huge selections, the lowest prices, and excellent customer care and service.

Lab diamond polish and symmetry frequently asked questions

Conclusion

Understanding lab diamond polish and symmetry is crucial when shopping for lab-grown diamonds. A high-quality polish enhances a diamond’s sparkle, while symmetry maximizes its light performance. The GIA grading methodology helps assess the quality of both factors, and it’s essential to examine your own lab-grown diamond before making a purchase.

When buying diamonds, it is essential to look for both good symmetry and polish features. In addition, it’s always best to buy from reputable jewelers who can provide you with diamond certificates that include detailed information about the diamond’s cut, carat weight, clarity, color grade, and other important characteristics.